pub fn dp_rec_mc(mut amount: u32) -> u32 {
    //1,2,5,10,20,30,100
    let mut num = 0;
    while amount > 0 {
        if amount >= 100 {
            amount -= 100;
        } else if amount >= 30 {
            amount -= 30;
        } else if amount >= 20 {
            amount -= 20;
        } else if amount >= 10 {
            amount -= 10;
        } else if amount >= 5 {
            amount -= 5;
        } else if amount >= 2 {
            amount -= 2;
        } else {
            amount -= 1;
        }
        num += 1;
    }
    num
}
